[js] Enable the signature binder on the js backend.
[js] Enable the signature binder on the js backend.

softmoth/rakudo,salortiz/rakudo,tbrowder/rakudo,tony-o/rakudo,tbrowder/rakudo,salortiz/rakudo,MasterDuke17/rakudo,nbrown/rakudo,rakudo/rakudo,tbrowder/rakudo,softmoth/rakudo,tony-o/rakudo,nbrown/rakudo,labster/rakudo,salortiz/rakudo,rakudo/rakudo,Gnouc/rakudo,tbrowder/rakudo,Gnouc/rakudo,rakudo/rakudo,Gnouc/rakudo,nbrown/rakudo,labster/rakudo,labster/rakudo,tbrowder/rakudo,tony-o/rakudo,tony-o/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,softmoth/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,labster/rakudo,tony-o/rakudo,rakudo/rakudo,salortiz/rakudo,labster/rakudo,nbrown/rakudo,rakudo/rakudo,Gnouc/rakudo,nbrown/rakudo,softmoth/rakudo,Gnouc/rakudo,rakudo/rakudo,salortiz/rakudo,labster/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,tony-o/rakudo,salortiz/rakudo,softmoth/rakudo,nbrown/rakudo